Reactivating a copper catalyst by treating with sodium chloride solution



Patented Sept. 20, 1949 REACTIVATING A COPPER CATALYST BY SODIUMCHLORIDE SO- TREATING WITH LUTION Wesley William Riches, Newport, DBL,assignor to E. I. du Pont de Nemours & Company,

mington, Del., a corporation of Delaware No Drawing. Application January29, 1947, Serial No. 725,154

. 6 Claims. 1

This invention relates to the production of titanium tetrachloride, andmore particularly to the reactivation of copper metal employed in thepurification of that compound.

Titanium tetrachloride is commonly prepared by the action of chlorine ontitanium-bearing ores, such as ilmenite and rutile. During thechlorination other volatile chlorides, particularly those of silicon,iron, and vanadium, are also formed, and must be removed from thetitanium tetrachloride before it can be usefully employed commercially.Partial purification and separation of compounds, such as ferricchloride and silicon tetrachloride, which have boiling pointsappreciably removed from that of titanium tetrachloride, may beaccomplished by fractional distillation, but more complex methods arerequired for the separation of the vanadium chlorides. In the copendingapplication of I-Iolger H. Schaumann, Serial No. 661,914, filed April12, 1946, pure, water-white titanium tetrachloride, substantially freefrom vanadium and other impurities, is obtained by distilling an impureform of such product over metallic copper (in the form of discreteparticles, such as scrap, heavy copper turn ings, borings, copperRaschig rings, etc.) as a con-tact mass. Periodically such mass must bereactivated by treatment with a non-oxidizing solution of an inorganicor organic acid, preferably dilute hydrochloric acid.

Acid treatment to reactivate the copper contact mass in the abovepurification operation, though highly useful and efficient, isrelatively expensive and hence economically unattractive for use from acommercial standpoint. For example, even though a non-oxidizing acid isemployed in the treatment, appreciable quantities of copper metal areremoved during such treatment which obviously shortens the life of thecopper contact mass. Additionally, the limited solubility of CuClrenders the process. somewhat time-consuming and considerable quantitiesof acid are required to be used. Furthermore, the recovery of thevaluable constituents from the solutions used in the leach is relativelyexpensive, due to the fact that relatively large amounts of acid must beneutralized.

It is the object of this invention to overcome these and otherdisadvantages which have characterized prior methods for reactivatingcopper contact masses employed in titanium tetrachloride purifications,and to provide novel methods for attaining such objects. Further objectsinclude: effecting such reactivation while minimizing loss of copperfrom the metallic mass; re-

moving met-a1 chloride impurities from the sur-- faces of the coppercontact mass, and attaining maximum reactivation of the metal forfurther use; and providing a novel method for effecting in particularsubstantially complete removal of vanadium and copper chlorides from thesurfaces of the contact mass, with accompanying advantageous recovery ofuseful forms of both copper and vanadium as valuable icy-products. Otherobjects and advantages of the invention will be apparent from thefollowing description thereof:

These and other objects are attained in this invention which comprisesreactivating a copper contact mass employed in titanium tetrachloridepurification by treatment with a solution of sodium chloride.

In a more specific and preferred embodiment, the invention comprisesreactivating a copper contact mass in the form of discrete pieces andcontaining a coating of copper and vanadium chlorides as impurities, bysubjecting said mass to the action of a saturated solution of sodiumchloride.

In practically applying the invention, in accordance with one preferredadaptation wherein titanium tetrachloride is distilled in a conventionaltype distillation column packed with a contact mass, such as copperRaschig rings, over and through which the vaporized TiCh is passed, saidcolumn is drained as dry .as possible at the end of the distillationperiod and when contamination of said mass is observed by reason of theexistence of a black coating of copper and vanadium chlorides thereover.Trapped liquids are removed by blowing out the column with an inert gasand until said column is substantially free from volatile chlorides.This pre-cleaning procedure is preferable, though not essential to thepractice of the invention, since it results in a more economical processand loss is thereby averted of considerable quantities of titaniumtetrachloride, as well as contamination prevented of the vanadium andcopper chlorides to be recovered. A sodium chloride solution, preferablysaturated, is then circulated through the distillation column and untilthe copper rings have lost their black coating and appear bright andmetallic. If desired, separate, repeated washing with fresh solutions ofthe chloride may be resorted to, or a wash solution may be recirculatedthrough the column. Preferably, use is avoided of an air lift or airagitation in the treating and cleaning operation, since the presence ofappreciable amounts of oxygen induces oxidation of' the cuprous chlorideto the cupric state and subsequent attack upon the fresh copper metal.After the treatment, the salt solution is drained from the column andthe latter may then be dried, after which it is ready for reuse in thepurificationoperation. As a result of such treatment, the copper isequally as efiective in purifying the titanium tetrachloride as it wasoriginally,

and can be used for another prolonged period before further activationtreatment will-be again required.

Alternatively, the vanadium chlorides present, being quite soluble inwater, can, if desired, be removed first by resorting to a water wash,following which .the copper chlorides can be removed from the rings bymeans of the sodiumchloride parts of a saturated sodium chloridesolution were thereupon recirculated through the column for a period ofthree hours, after which the column Fwas drained and dried by ,passingWarm air through it, and distillation therein of titanium treatmentherein contemplated. This modification of my invention will require alonger period, however, and hence is not preferred, being lesseconomical than the single-step operation where- V in all of thechlorides are removed together in the sodium chloride treatment.

The solution recovered from the washing or leaching operation willcontain substantial amounts of vanadium chlorides and a complex ofcopper and sodium chlorides, together with small amounts of chlorides oftitanium and iron. These can be easily separated and recoveredbyconventionally-known methods.

The examples below, in which the parts used are by weight, are given asillustrations of methods of carrying out this invention, and are not tobe construed as limitations thereof:

Example 1 A conventional glass distillation column was packed with 665parts of A" copper Raschig rings. 20,611 parts of titaniumtetrachloride, previously distilled to remove most ofthe lowerboilingcompounds and iron chloride, and containing 1270 parts of vanadium permillion, were vaporized and fed through this packed column. A'pure,water-white distillate product was obtained until near the endof theoperation, when the rings became coated and the distillate producedbecame yellow in color. -At this point, the column was drained, and drynitrogen was blown through it for half an hour toremove the remainingtitanium tetrachloride from the column packing. 300 parts of asaturatedsodium chloride solution were then circulated through thecolumn for an hour, by means of a'nitrogen lift. This procedure wasrepeated twice, using fresh sodium chloride solutions in each instance.The column was then rinsed with 650 parts of water, dried, and TiCl4distillation resumed, to obtain again a pure, water-white titaniumtetrachloride distillate.

The copper rings weighed 609 parts after this treatment, losing 56parts, or 8.4% of their original weight, during the distillation andtreatment. By analysis, the first leach solution contained 36.7 parts ofcopper; the second 15.8 parts;

the third, 3.4 parts, and the wash water, 0.! part. jThis totalled 56.6parts of copper recovered, which was slightly more than the loss inweight of the copper packing.

7 Example II A distillation apparatus similar to that used in Example Iwas packed with 608 parts of A," copper Raschig rings. 22,500 parts ofpre-distilled titanium tetrachloride, containing 912 parts per millionof vanadium, were distilled through the column. A water-whitedistillate, containing approximately 1 part of vanadium per million, was

tetrachloride was resumed. A water-White distillate'containing less than1 part per million of vanadium was again recovered.

, a The sodium chloride solution used for cleaning the column was foundto contain 68 parts of cop-' per and 20 parts of vanadium.

While described above as applied to certain preferred embodiments, theinvention is not limited thereto, since it may be varied therefromwithout departing from its underlying principles and scope. The choiceof an exact process will depend on the demands of a particularapplication. Thus, while impurity removal from the copper can beefiected by simply soaking the contact mass in a sodium chloridesolution, such removal is advantageously accelerated if the treatingsolution is agitated. Thus, a non-oxidizing gas, such as notrogen,hydrogen, or other gas inert toward the copper and treating solution canbe bubbled through the solution during its contact with the copper andwill be found to improve the rate of cleaning considerably. As alreadynoted, oxidizing gas use should be avoided,since it'promotes attack ofthe copper metal itself. In

' lieu of immersion of'the contact mass in the solution, the latter may,if desired, be sprayedover such mass, either continuously orintermittently during the cleaning operation. More or less con 'tinuouscirculation of the cleaning solution through the vessel and over thecontact mass is the most effective method, and hence this method ofcleaning is preferred. In some instances, the contact mass may beremoved from the apparatus and treated in accordance with theinvention-in.

a separate vessel. 'In such event, tumbling bar rels, scrubbingmechanisms, and similar devices can be restorted to in order tofacilitate the de-'- sired cleaning operation.

Although, as stated in the above example, I prefer to remove as much aspossible of the titanium tetrachloride adhering to the copper con tactmass before introducing the cleaning solution,'this is simply aneconomic measure, to cone serve the titanium tetrachloride.

7 Any of this material remaining on the copper will be removed in thewash solution, and hence can subsequently be separated and recoveredfrom the vanadium and copper, if desired. 7

Again, while the use of a' saturated or relatively of sodium chlorideper liter, and hence, some sacrifice in the efliciency of the washingoperation may result.

After treatment of the contaminated copper contact mass, in accordancewith my invention, it will become thoroughly cleaned, and will proveequally as effective during use in the subsequent purification oftitanium tetrachloride, and will accomplish removal of vanadiumcompounds, with as much facility and completeness as a similar charge ofnew copper metal. The cleaning operation is simple and quick, requiringonly the most inexpensive materials, and can be readily carried outwithout removing the copper contact mass from the distillationapparatus. The unused copper is not appreciably attacked by the cleaningsolution, so that little or no copper loss is incurred over the amountof copper required to remove the vanadium compounds from the titanium.tetrachloride. The residual copper and vanadium compounds from thetreatment are in relatively concentrated form and in a salt solutionfrom which they can be easily recovered without the necessity ofresorting to neutralization of large quantities of cleaning acids withthe reagents which precipitate the copper and vanadium compounds. Thesolutions remaining after copper and vanadium extraction will usuallycomprise fairly pure, concentrated brine, which can be used forsubsequent cleaning operations, either as is, or with very littleadditional treatment.

The particular efiectiveness of my treatment in reactivating a metalliccopper contact mass appears to arise from the formation of a sodiumchloride-cuprous chloride complex during the sodium chloride treatmentwhich is soluble in water and is readily removed in the final rinsingoperation. Cuprous chloride is only slightly soluble in water, itssolubility at 25 C. being of the order of 15 grams per 1000 grams ofwater. At the same temperature, its solubility in a saturated sodiumchloride solution is approximately 500 grams per 1000 grams of water,while only about 150 grams of cuprous chloride will dissolve in 1000grams of a dilute (20%) hydrochloric acid solution.

I claim as my invention:

1. A method for reactivating a copper contact mass and removing metalchloride contaminants therefrom which comprises subjecting said mass tothe action in the absence of appreciable amounts of oxygen of a solutionof sodium chloride, at a concentration of at least 200 g./1. NaCl untilsaid chloride contaminants are dissolved in said solution, and thendrying the purified mass prior to reuse.

2. A method for reactivating a copper contact mass and removing metalchloride contaminants therefrom which comprises subjecting said mass tothe action in the absence of appreciable amounts of oxygen of asaturated solution of sodium chloride, until said contaminants aredissolved in said solution, and. then drying the purified mass prior toreuse.

3. A method for reactivating a vanadium chloride-contaminated coppercontact mass utilized in titanium tetrachloride purification whichcomprises soaking said mass in the absence of appreciable amounts ofoxygen in a concentrated sodium chloride solution to efiect removal ofthe contaminant, and removing said solution from the treated mass bywater rinsing and drying said mass prior to its reuse.

4. A method for reactivating a vanadium chloride-contaminated coppercontact mass employed in a distillation column, which comprises passinga saturated sodium chloride solution through said column and over saidmass for a sufiicient period of time to effect the removal ofcontaminant present on said mass, and then water rinsing and drying thetreated mass prior to reuse.

5. A method for removing contaminant metal chlorides from a coppercontact mass employed in titanium chloride purification which comprisessoaking and washing said mass in the absence of appreciable amounts ofoxygen in a saturated sodium chloride solution until said metalcompounds are dissolved in said solution, and then water rinsin anddrying the treated mass prior to reuse.

6. A method for removing vanadium and copper chlorides from a coppercontact mass in which said chlorides are present as contaminants whichcomprises washin said mass in the absence of appreciable amounts ofoxygen with a circulated concentrated sodium chloride solution untilsubstantially all of said copper and vanadium compounds are dissolved,separating the resulting solution from the said mass, and then waterrinsing and drying the treated mass prior to reuse.

WESLEY WILLIAM RICHES.

file of this patent:

Mellor, Treatise on Inorganic and Theoretical Chemistry, vol 3, page 162(1923)

